Reaction mechanism of dimethyl ether carbonylation to methyl acetate over mordenite – a combined DFT/experimental study

Rasmussen, Dominik Bjørn; Christensen, Jakob Munkholt; Temel, Burcin; Studt, Felix; Moses, Poul Georg; Rossmeisl, Jan; Riisager, Anders; Jensen, Anker Degn

doi:10.1039/c6cy01904h

Cited by 63 publications

(85 citation statements)

References 52 publications

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“…The calculation results revealed that a feasible reaction temperature and pressure exist in the range 573-598 K and 50-65 bar, respectively ( Figure 6). Although different from the condition for DME carbonylation reported in literature (usually below 450 K and 20 bar [20,21]), the finding seemed to be compatible with our test condition. comparable to or a little higher than those of any hybrid/bifunctional catalysts reported in literature (cf.…”

Section: Attempts To Improve the Selectivity To Dmesupporting

confidence: 78%

“…The calculation results revealed that a feasible reaction temperature and pressure exist in the range 573-598 K and 50-65 bar, respectively ( Figure 6). Although different from the condition for DME carbonylation reported in literature (usually below 450 K and 20 bar [20,21]), the finding seemed to be compatible with our test condition. The activity test was performed in a dual-bed catalyst system using the SP-derived catalyst and zeolite ferrierite (FER@FER) recently developed by a seed method [22], where the latter catalyst of 2.0 g was placed right after the bed of 0.6 g SP-60 or SP-80 ( Table 5).…”

Section: Attempts To Improve the Selectivity To Dmesupporting

confidence: 78%

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Direct Conversion of CO2 into Dimethyl Ether over Al2O3/Cu/ZnO Catalysts Prepared by Sequential Precipitation

Jeong

Kim

et al. 2019

Catalysts

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Bifunctional Al2O3/Cu/ZnO catalysts with Al composition of between 30 mol% and 80 mol% were prepared by sequential precipitation (SP) for the conversion of CO2 into dimethyl ether (DME). In the SP synthesis, the concentration of a precipitation agent managed to be high enough to induce the complete precipitation of Al3+. The prepared precipitates were composed of zincian malachite and amorphous AlO(OH). Furthermore, the calcined mixed metal oxide materials of 60% and 80% Al exhibited a higher acidity than commercial Al2O3 and the H2-reduced catalysts showed the similar Cu dispersion of 6%–7% at all Cu loadings. In the activity test at 573 K and 50 bar, the SP-derived catalyst of 80% Al (SP-80) displayed the best performance corresponding to CO2 conversion of 25% and DME selectivity of 75% that are close to equilibrium values. In order to overcome the thermodynamic limitation, a dual-bed catalyst system was made up of SP-80 in the first layer and zeolite ferrierite in the next. This approach enabled DME selectivity to be enhanced to 90% while CO2 conversion increased a little. Consequently, the studied catalyst system based on the SP-derived catalysts can contribute greatly to selective DME production from CO2.

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Section: Attempts To Improve the Selectivity To Dmesupporting

confidence: 78%

“…The calculation results revealed that a feasible reaction temperature and pressure exist in the range 573-598 K and 50-65 bar, respectively ( Figure 6). Although different from the condition for DME carbonylation reported in literature (usually below 450 K and 20 bar [20,21]), the finding seemed to be compatible with our test condition. The activity test was performed in a dual-bed catalyst system using the SP-derived catalyst and zeolite ferrierite (FER@FER) recently developed by a seed method [22], where the latter catalyst of 2.0 g was placed right after the bed of 0.6 g SP-60 or SP-80 ( Table 5).…”

Section: Attempts To Improve the Selectivity To Dmesupporting

confidence: 78%

Direct Conversion of CO2 into Dimethyl Ether over Al2O3/Cu/ZnO Catalysts Prepared by Sequential Precipitation

Jeong

Kim

et al. 2019

Catalysts

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“…Theoretical studies have been employed to calculate reaction free energy barriers of possible initiation and C-C coupling steps to shed light on plausible reaction mechanisms [43][44][45][46][47][48][49][50][51][52][53][54][68][69][70]. Using H-SSZ-13 as the catalyst we recently proposed a viable mechanism of the initiation reaction based on DFT calculations that have been corrected using second order Møller Plesset perturbation theory (MP2) [71] thus comprising highly accurate reaction barriers [72].…”

Section: Supplementary Informationmentioning

confidence: 99%

Effect of Impurities on the Initiation of the Methanol-to-Olefins Process: Kinetic Modeling Based on Ab Initio Rate Constants

2021

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The relevance of a selection of organic impurities for the initiation of the MTO process was quantified in a kinetic model comprising 107 elementary steps with ab initio computed reaction barriers (MP2:DFT). This model includes a representative part of the autocatalytic olefin cycle as well as a direct initiation mechanism starting from methanol through CO-mediated direct C–C bond formation. We find that the effect of different impurities on the olefin evolution varies with the type of impurity and their partial pressures. The reactivity of the considered impurities for initiating the olefin cycle increases in the order formaldehyde < di-methoxy methane < CO < methyl acetate < ethanol < ethene < propene. In our kinetic model, already extremely low quantities of impurities such as ethanol lead to faster initiation than through direct C–C bond formation which only matters in complete absence of impurities. Graphic Abstract

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“…We postulate that the non-linearity in these rates as a function of Si/Al originates from the sensitive relationship between MA rates and methoxy location, as evidenced by prior experimental and computational work in MOR. 6,9,17,43 This relationship arises from the stabilization (or lack thereof) via confinement of the transition state formed by CO attack on the methoxy group, which decreases (or increases) the activation barrier of the RDS. There are three primary positions for monovalent, extraframework cations to site in SSZ-13 ( Figure 7) associated with the crystallographically-distinct O atoms.…”

Section: Cha: Activity Vs Si/almentioning

confidence: 99%

Carbonylation of Dimethyl Ether to Methyl Acetate over SSZ-13

et al. 2019

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The small-pore zeolite with the chabazite framework topology, SSZ-13, is found to be an active catalyst in the carbonylation of dimethyl ether to methyl acetate (MA). The production of MA over SSZ-13 after 24 h on stream at 165 °C and 1 bar approaches that obtained from mordenite and is significantly higher than from ferrierite at comparable Si/Al of ca. 10. To understand the origin of the activity, SSZ-13 materials are synthesized with variable Si/Al, characterized via several techniques including multinuclear magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, and evaluated for their carbonylation activity. While MA production rates increase with decreasing Si/Al, the correlation is nonlinear due to the effect of Si/Al on the acid site distribution within different confining environments, and the associated impact of the latter on the rate-determining transition state barrier. Enhanced MA production rates trend with acid sites located at the eight-membered ring (8MR) that are increasingly populated as framework Al content increases. Density functional theory analyses of transition state energies as a function of active site location support the experimental findings, where the lowest apparent barriers are associated with the methoxy groups that orient within the plane of the 8MR window. This is due to an optimal charge stabilization of the cationic transition states with the negatively charged oxygens within the 8MR window. The effects of catalyst chemical composition, separate from framework topology, are also investigated using SAPO-34 (the silicoaluminophosphate analog of SSZ-13). Analyses of the 1 H MAS NMR signals and carbonylation activity suggest that the higher acid site strength of SSZ-13 compared to that of the SAPO material is required for effective Brønsted acid catalysis of Koch-type carbonylation pathways.

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Reaction mechanism of dimethyl ether carbonylation to methyl acetate over mordenite – a combined DFT/experimental study

Abstract: Dimethyl ether carbonylation to methyl acetate over mordenite was studied theoretically with density functional theory calculations and experimentally in a fixed bed flow reactor. A new reaction path to methyl acetate entirely in the 8 membered ring was discovered.

Cited by 63 publications

References 52 publications

Direct Conversion of CO2 into Dimethyl Ether over Al2O3/Cu/ZnO Catalysts Prepared by Sequential Precipitation

Direct Conversion of CO2 into Dimethyl Ether over Al2O3/Cu/ZnO Catalysts Prepared by Sequential Precipitation

Effect of Impurities on the Initiation of the Methanol-to-Olefins Process: Kinetic Modeling Based on Ab Initio Rate Constants

Carbonylation of Dimethyl Ether to Methyl Acetate over SSZ-13

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